Okay, so basically Murasaki used to be a Tsuchinoto in the Demon Slayer Corps. (It’s like the 5th rank, I believe). So once she had to go out on a mission in some mountains and fight some pretty strong demons, as in some of the 12 Demon Moons. So she was in the mountains with the company of a few other Tsuchinoto and two Kanoe. On the way up the mountains, they got ambushed by 3 of the 12 Demon Moons, and only one Kanoe survived to return back and tell the story until they were hunted down and killed. Murasaki was killed. She and the other demon slayers came back as demons, and proceeded to inhabit that mountain area. But because of the way they came back, they were pretty tame demons. So then some demon slayers went back to the mountains, and found the tame demons. They were brought back and the Demon Slayer Corps decided to keep them since they weren’t sure of what they were capable of. Twiilight helped me come up with the idea of Murasaki dying and coming back as a demon, so props to her.